Enterobacter /En·tero·bac·ter/ (en´ter-o-bak?ter) a genus of gram-negative, facultatively anaerobic rod-shaped bacteria of the family Enterobacteriaceae, widely distributed in nature and occurring in the intestinal tract of humans and animals. Species including E. aero´genes, E. agglo´merans, E. cloa´cae, and E. gergo´viae, are frequently the cause of nosocomial infection, arising from contaminated medical devices and personnel.

In a 1981 study, “Enteral feeds contaminated with Enterobacter cloacae as a cause of septicaemia,” M.W. CASEWELL, et al., reported, “Artificial enteral feeds are increasingly used for patients withsevere catabolic states associated with, for example, bowel pathology, burns, infection, and malignancy.One advantage claimed for using this route is the "virtual absence of the risk of infection."' Despite ourprevious study which showed that contaminated enteral feeds were a source of Klebsiella spp forintensive care patients,2 a recent Drugs and Therapeutics Bulletin on enteral feeding does not mentionthe hazard of infection.3 We report on a patient with septicaemia caused by Enterobacter cloacaederived from enteral feeds that had been contaminated by a detergent dispenser in a diet kitchen. – Thiscase illustrates how contaminated enteral feeds provide a source of opportunistic Gram-negative bacillithat may colonise or seriously infect debilitated patients. Such organisms multiply readily at roomtemperature, and there are thus advantages of using commercially produced bacteriologically cleanfeeds, which do not require mixing with additives or diluents in the hospital environment, anddisadvantages of continuous infusion of mixed feeds over several hours at room temperature. Wesuspect that other hospitals are similarly contaminating enteral feeds during their preparation andsuggest that the unsuspected, but avoidable, infection hazards of this common form of treatmentshould be more widely recognised.”http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1504797/pdf/bmjcred00650-0047.pdf

In a 1987 study, “Outbreak of cephalosporin resistant Enterobacter cloacae infection in a neonatalintensive care unit,” N. Modi, et al., reported, “Enterobacter cloacae resistant to third generationcephalosporins emerged rapidly during an outbreak of serious infections due to this organism in aneonatal intensive care unit where ampicillin and gentamicin were used as first line antibiotictreatment. Organisms resistant to cephalosporins were isolated from 12 infants, six of whom developedsystemic infection. Two infants died. Isolates of E. cloacae from four of five infants treated withcefotaxime showed a loss of sensitivity to this antibiotic during treatment, but in the three infants whosurvived sensitive organisms were again isolated after treatment had stopped. Stopping treatment withthe cephalosporins, closure of the unit to new admissions, and strict cohorting of colonised infantsresulted in a prompt end to the outbreak. This outbreak suggests that the routine use of third generationcephalosporins for suspected sepsis may be inappropriate in the presence of a large reservoir oforganisms with the potential for rapidly developing resistance. Routine bacteriological surveillance,however, might permit their use on a rotational basis.” http://adc.bmj.com/content/62/2/148.abstractIn the 1998 study, “Occurrence of Virulence-Associated Properties in Enterobacter cloacae,” RogériaKeller, et al., Universidade Federal de São Paulo, reported, “Enterobacter cloacae is part of the normalflora of the gastrointestinal tract of 40 to 80% of people and is widely distributed in the environment(15, 19, 39). Like most members of the family Enterobacteriaceae, these organisms are capable ofcausing opportunistic infections in hospitalized or debilitated patients (18, 19). They were recognizedas a minor cause of hospital infection in a survey published in 1981 (31). Since then, clinical awarenessof the potential of E. cloacae strains to cause disease has been reflected in the increasing number ofepidemiologic studies of these microorganisms showing that they could be a serious cause ofnosocomial gram-negative bacteremia (9, 17-19, 23).” http://iai.asm.org/cgi/content/full/66/2/645

In the 1999 study, “Outbreak of Enterobacter cloacae Related to Understaffing, Overcrowding, andPoor Hygiene Practices,” Stephan Harbarth , MD, MS, et al., University Hospitals of Geneva, stated a“Retrospective cohort study in a neonatal intensive‐care unit (NICU) from December 1996 to January1997; environmental and laboratory investigations. – 60 infants hospitalized in the NICU during theoutbreak period. – Of eight case‐patients, two had bacteremia; one, pneumonia; one, soft‐tissueinfection; and four, respiratory colonization. – Several factors caused and aggravated this outbreak: (1)introduction of E cloacae into the NICU, likely by two previously colonized infants; (2) furthertransmission by HCWs’ hands, facilitated by substantial overcrowding and understaffing in the unit; (3)possible contamination of multidose vials with E cloacae. Overcrowding and understaffing in periodsof increased work load may result in outbreaks of nosocomial infections and should be avoided.”http://www.jstor.org/stable/30142031

In a 2000 study, “Detection of Extended-Spectrum -Lactamases in Clinical Isolates of Enterobactercloacae and Enterobacter aerogenes,” Eva Tzelepi, et al., Hellenic Pasteur Institute at Athens, said,“The aim of the present study was to investigate the frequency of extended-spectrum -lactamases(ESBLs) in a consecutive collection of clinical isolates of Enterobacter spp. The abilities of variousscreening methods to detect ESBLs in enterobacters were simultaneously tested. Among the 68consecutive isolates (56 Enterobacter cloacae and 12 Enterobacter aerogenes isolates) that wereanalyzed for -lactamase content, 21 (25 and 58%, respectively) possessed transferable ESBLs with pIsof 8.2 and phenotypic characteristics of SHV-type enzymes, 8 (14.3%) of the E. cloacae isolatesproduced a previously nondescribed, clavulanate-susceptible ESBL that exhibited a pI of 6.9 and thatconferred a ceftazidime resistance phenotype on Escherichia coli transconjugants, and 2 E. cloacaeisolates produced both of these enzymes. Among the total of 31 isolates that were considered ESBLproducers, the Vitek ESBL detection test was positive for 2 (6.5%) strains, and the conventionaldouble-disk synergy test (DDST) with amoxicillin-clavulanate and with expanded-spectrumcephalosporins and aztreonam was positive for 5 (16%) strains. Modifications of the DDST consistingof closer application of the disks (at 20 instead of 30 mm), the use of cefepime, and the use of bothmodifications increased the sensitivity of this test to 71, 61, and 90%, respectively. Of the 37 isolatesfor which isoelectric focusing failed to determine ESBLs, the Vitek test was false positive for 1 isolateand the various forms of DDSTs were false-positive for 3 isolates.”http://www.ncbi.nlm.nih.gov/pmc/articles/PMC86144/

In a 2003 study, “Nosocomial Enterobacter Meningitis: Risk Factors, Management, and TreatmentOutcomes,” Stephen Parodi, et al., Veterans Affairs Greater Los Angeles Healthcare System, reported,“Enterobacter species are increasingly a cause of nosocomial meningitis among neurosurgery patients,but risk factors for these infections are not well defined. A review of all adult patients hospitalized atthe University of California-Los Angeles (UCLA) Medical Center during an 8-year period identified 15postneurosurgical cases of Enterobacter meningitis (EM). Cure was achieved in 14 cases (93%), andefficacy was similar for carbapenem- and cephalosporin-based treatment. – Although uncommon, theproportion of cases of nosocomial meningitis due to gram-negative organisms appears to be increasing[1–3]. Appropriate empirical antimicrobial therapy for the treatment of gram-negative bacillarymeningitis is essential to prevent morbidity and mortality [3, 4], and treatment options are limited byemerging resistance to third-generation cephalosporins, especially among Enterobacter species [5–7].”http://cid.oxfordjournals.org/content/37/2/159.full

The 2011 Austin Community College Microbology for the Health Sciences report on “Enterbactercloacae," [states] Enterobacter bacteria are nosocomial opportunistic pathogens that cause infections thatinclude~5% of hospital-acquired septicemias~5% of nosocomial pneumonias~4% of nosocomial urinary tract infections~10% of postsurgical peritonitis casesSome usefulness to humans, such as E. cloacae used in biological control of plant diseases.”http://www.austincc.edu/rlewis3/docs/g-neg-info.html

Enterobacter in Plants

In 1982, John M. Gardner, et al., University of Florida at Lake Alfred, reported on “Bacteria in RoughLemon Roots of Florida Citrus Trees.” They said, “An aseptic vacuum extraction technique was used toobtain xylem fluid from the roots of rough lemon (Citrus jambhiri Lush.) rootstock of Florida citrustrees. Bacteria were consistently isolated from vascular fluid of both healthy and young tree declineaffected[dying] trees. Thirteen genera of bacteria were found, the most frequently occurring generabeing Pseudomonas (40%), Enterobacter (18%), Bacillus, Corynebacterium, and other gram-positivebacteria (16%), and Serratia (6%). Xylem bacterial counts fluctuated seasonally. Bacterial populationsranged from 0.1 to 22 per mm3 of root tissue (about 102 to 2 x 104 bacteria per g of xylem) whenbacterial counts were made on vascular fluid, but these numbers were 10- to 1,000-fold greater whenaseptically homogenized xylem tissue was examined similarly. Some of the resident bacteria (4%) arepotentially phytopathogenic. It is proposed that xylem bacteria have an important role in the physiologyof citrus.”http://aem.asm.org/cgi/content/abstract/43/6/1335

In the 1993 article, “Enterobacter cloacae: internal yellowing of papaya (Plant Disease Pathogen),”K.A. Nishijima, University of Hawaii, said, “Enterobacter cloacae has been isolated from papayaflowers, homogenates of papaya seeds, and the crop and mid-gut of the oriental fruit fly (Dacus dorsalisHendel), and recent studies claiming an apparent attractancy of D. dorsalis to E. cloacae, suggest thatfruit flies may possibly be involved in the transmission of the bacterium to papaya. -- A report of E.cloacae isolated from homogenates of papaya seeds in 1972 suggests that this organism may have beenpresent in a non-pathogenic form for many years. Monthly samplings from five papaya packinghouses,that process fruit from different areas on the island of Hawaii, indicate that the incidence of internalyellowing is sporadic and may be affected by environmental factors.”http://www.extento.hawaii.edu/kbase/crop/type/e_cloac.htm

Enterobacter: several species cause opportunistic infections of the urinary tract as well as other parts of the body.E. aerogenes and E. cloacae are two such pathogens that do not cause diarrhea, but that are sometimes associatedwith urinary tract and respiratory tract infections.

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